This invention is directed to a system whereby a semi-trailer is inhibited against theft by thrusting a plunger in the way of access to the semi-trailer hitch.
Semi-trailers are widely used in modern transportation of goods. These semi-trailers are provided with a hitch pin which selectively engages in and is releasably locked in the fifth wheel of a truck or tractor. When a semi-trailer loaded with cargo is parked, it is susceptible to theft by the simple engagement by a new truck. One useful way of preventing unauthorized removal of a semi-trailer is by the maintaining of the brakes in the locked condition by closing and locking a valve which prevents release of air from the brake line. Such a system is disclosed in patent application Ser. No. 530,530, entitled "Truck Trailer Brake Air Line Lock," filed Sept. 9, 1983 by John M. Murray, the entire disclosure of which is incorporated herein by this reference. Such a system greatly enhances the antitheft characteristics of a semi-trailer, but does not inhibit the hitching up of a truck to the hitch pin of a semi-trailer. Thus, it is desirable to further improve the security of semi-trailers.